Investigations have failed to find any evidence so far of agricultural chemicals buried under a South Canterbury lake.
Canterbury Regional Council tested water, fish and sediment samples at the lake after claims that drums of DDT and other pesticides were dumped at hydroelectric dam site during its construction in the 1990s.
The council's surface water resources and ecosystems manager, Dr Tim Davie, says sonar studies found no evidence of buried drums in Lake Opuha and no pesticides were found in any of the water samples.
Traces of pesticides were found in sediment, fish and eels, from the lake, he says, but were consistent with other samples taken around Canterbury.
Dr Davie says the results confirm Lake Opuha is safe for fishing and recreational use, but the council will continue pesticide sampling there to monitor any changes.